1. Field of the Invention
The present invention concerns a container having an overpressure safety device, and, more particularly, a container having a depression that is capable of expanding radially when the pressure inside the container exceeds a predetermined level and that is restrained angularly by a clamp bridging over the depression.
2. Description of Related Art
Closed containers may explode when a gaseous material generated or contained inside the container increases in pressure beyond a predetermined level. Such a pressure increase may occur for a variety of reasons. For example, in electrical capacitors, gas may be generated by an electro-chemical decomposition process caused by the aging of the capacitor or by an improper usage of the capacitor. Such an increase in the internal pressure may be so rapid that an explosion of the capacitor may occur.
In the prior art, a weaker mechanical point is introduced in the capacitor container, so that a container wall opens incrementally when the internal pressure exceeds a predetermined level, that is, reaches an “overpressure” condition. If the container is tubular in shape, with a base and a cap enclosing the contained material, such a weaker mechanical point may be shaped like a longitudinal groove positioned on the tubular wall, or on the base or on the cap of the container. Such a groove is sometimes referred to in the industry as a “fuse” and may be provided by causing a local reduction in wall thickness during the manufacture of the container, or by a stamping process, or by an appropriate shaping of the tubular wall if the tubular wall is produced by extrusion, or by other methods.
Such a system of overpressure prevention system is not optimal. In the event of overpressure, the soft opening of the fuse is inversely proportional to capability of the fuse to expand under dynamic pressure conditions, and when the rate of pressure increase exceeds the soft opening capability of the fuse, the container wall may tear rapidly and the container may explode.
A solution to this problem may lay in increasing the thickness of the wall can, but that also causes an increase in container weight and cost, and also causes manufacturing problems when the cap is put on the container and joined with the tubular wall.
Therefore, there is a need for a container having an overpressure safety device enabling the container to expand incrementally while preventing an explosion of the container.